It is well-known to secure a motor vehicle against operation by a person who has consumed alcohol by installing in said vehicle a breath alcohol tester. A typical arrangement, known as an ignition interlock device (IID), involves a relay between the breath tester and the starter motor, pursuant to which the starter motor cannot be engaged until a satisfactory breath sample has been given. In this regard, a ‘satisfactory’ gas sample is conventionally understood to be one that (i) is of sufficient volume and pressure to permit alcohol analysis; (ii) has alcohol concentration below a predetermined limit; and (iii) appears to have originated from the exhaled breath of a human being. Criteria (iii) is often assessed through measurements of pressure, humidity and temperature, but various other techniques such as hum recognition sensors are occasionally used. In some jurisdictions, a person convicted of driving under the influence of alcohol may be required by law to have a device of this type installed as a condition associated with the extension of driving privileges. While the engine is running, the IID will randomly require the driver to provide another breath sample. The time between required breath samples is dependent on the setting of the unit but it is typical for random breath samples to be required every 10 to 20 minutes while the vehicle is in operation. The purpose behind the random breath sample is to prevent a driver from having a “sober” friend blow into the device to start the vehicle and to deter drinking while driving. If the requested breath sample is not provided or exceeds the predetermined limit, the device will record the incident, warn the driver and then start up an alarm (e.g., lights flashing, horn honking, etc.) until the ignition is turned off or a satisfactory breath sample has been provided.